Craniotomy Closures and Plugs

ABSTRACT

Strip fasteners and cranial plugs for use in reattaching a skull flap removed during brain surgery and methods of using the same. The strip fasteners are flexible and can be shaped to follow the perimeter contour of the skull flap. The cranial plugs can be used to reattach the skull flap or they can be installed after the skull flap is reattached using the strip fasteners. In some embodiments, the cranial plug(s) and strip fasteners can be installed at the same time. The strip fasteners and cranial plugs are designed to encourage bone growth and healing of the skull flap and they can be used to deliver medication and bone growth enhancement compositions to the surgical site.

FIELD OF THE INVENTION

The invention relates to surgical strip fasteners, particularly for usein reattaching a skull flap removed during brain surgery, and methods ofreattaching the skull flap using the strip fasteners. The invention alsohas to do with cranial plugs used to fill small openings in the craniumor the burr holes made to facilitate cutting out a skull flap. In afurther aspect, the invention relates to surgical strip fasteners andcranial plugs and methods which enhance bone growth and the consequenthealing of the skull flap and the skull.

BACKGROUND OF THE INVENTION

Surgical access to the brain for neurosurgical procedures is created byremoving a portion of the patient's skull, a procedure termed acraniotomy. The craniotomy is determined by the location of thepathology within the brain, the safest/easiest access route and thedegree of exposure required for the procedure. Once the location isdetermined, the first step is to create an initial perforation of thefull thickness of the skull. Special skull perforators are available tocreate perfectly round holes but most surgeons simply use a rounded,end-cutting burr to create the perforation. Typically the perforation isin the range of about 11-15 millimeters (mm) in diameter. A surgeon maychoose to create more than one perforation around the perimeter of theplanned craniotomy. Some surgeons prefer a single perforation and othersuse more than one, but there is no standard number. Once this hole iscreated, it allows the insertion of a rotary powered surgical instrument(e.g., a craniotome) which is used to create a continuous cut (kerf)around the perimeter of the craniotomy. This kerf begins and ends at theperforation when there is one perforation or it runs from oneperforation to another when more than one perforation is made in theskull. The kerf is made with a side cutting burr which is shielded fromthe dura (outer covering of the brain) by a foot plate on thecraniotome. The foot plate extends below and forward of the cutting burrand the surgeon keeps the tip of the foot plate in contact with theinner surface of the skull as he performs the craniotomy. The typicalkerf is made freehand with an approximately 2 mm diameter burr. Theshape of the craniotomy is therefore highly variable and the kerf is notalways oriented perpendicular to the skull. The kerf may be larger than2 mm in some areas as well. Over the course of the kerf, the skullthickness will vary, typically over the range of 3-8 mm in adults.

Once the cut is complete, the skull flap is removed from the skull andplaced on the sterile back table for reinsertion at the end of theprocedure. After completion of the soft tissue surgery (typically 1-6hours), the skull flap is inserted back into the craniotomy and fixatedto prevent movement and restore the original contour of the skull. Thesurgeon may bias the skull flap toward one side or another to createbone-to-bone contact in a particular area or he may leave a gap aroundthe entire flap. The scalp is then closed and the patient is sent to theneurosurgical intensive care unit for recovery.

If complications develop while the patient is in the hospital, there maybe the need for emergency access to the brain through the craniotomysite. In addition, some patients may return for subsequent craniotomiesin the same region, particularly in cases of recurrent tumors.Postoperative imaging studies (MRI or CT) are generally conducted on allpatients. There is no clear evidence that the skull flap ever completelyheals (solid bony union) in adults. It is more likely that a combinationof new bone formation and fibrous connective tissue fills the gapbetween the skull and the skull flap.

From a surgeon's perspective, the method of reattaching the bone flapmust be safe, simple to use, be rapidly applied, permit emergentre-entry, not interfere with postoperative imaging studies, providestable fixation and have an acceptably low profile. The ideal methodwould result in complete fusion of the bone flap to the native skullwith no long term evidence of prior surgery.

Current methods of reattaching the skull flap include drilling a seriesof small holes in the edge of the skull and the edge of the flap.Sutures are then passed through the corresponding holes and the flap issecured back into the skull opening from which it was taken. Because thefit is not exact due to the material removed by the craniotome, the flapcan sag and sit slightly below the surface of the skull resulting in adepressed area that is obvious through the skin.

Another common reattachment method substitutes stainless steel wire forthe suture material and fewer holes are used. There is still the risk ofa cosmetically objectionable depressed area resulting. Metallic cranialfixation is (generally) only ever removed if it becomes symptomatic orif it interferes with subsequent surgeries.

More recently, surgeons have begun to use the titanium micro plates andscrews that were developed for internal fixation of facial and fingerbones. While this method results in a more stable and cosmetic result,it is relatively expensive, does not insure fusion and leaves foreignbodies at the surgical site.

All of these methods take ten minutes to one hour of additional surgeryafter the soft tissue (brain) surgery.

There is another method in which a titanium rivet (or clamp) is placedinside the skull with the stem of the rivet (clamp) passing between theskull and the flap. A large “pop rivet” type tool is used to force anupper titanium button down over the stem of the rivet, locking the flapand the skull in place between the upper and lower buttons. Three orfour of these rivets and buttons are used to secure the flap in place.This method can be faster than other methods and less expensive than thetitanium plates, but more expensive than sutures or wires. Just as withtitanium plates and screws, fusion is not assured and foreign bodiesremain in the patient.

According to the present invention we have developed new surgical stripfasteners and cranial plugs for, and methods of, reattaching a skullflap in a skull opening. The fixation provided utilizing a stripfastener and cranial plugs and practicing the methods of the inventionis secure and cosmetically acceptable. The strip fastener and plugs alsocan enhance bone growth, in a manner which causes healing by means ofbone-to-bone reattachment of the skull flap to the skull.

SUMMARY OF THE INVENTION

The surgical strip fasteners of the present invention are sufficientlyflexible that they can be shaped to follow the perimeter contour of theskull flap and, consequently, the perimeter contour of the opening inthe skull from which the flap was removed. This allows the surgeon toreattach the flap in generally the same position from which it wasremoved, thereby maintaining the contour of the skull in a manner whichis cosmetically desirable.

A strip or ribbon of material comprises the element of the stripfastener which is shaped to follow the perimeter contour of the skullflap. In most embodiments the strip fastener is provided with tabs orflanges which are disposed over and adjacent to the skull flap and theskull. The strip fastener also can be provided with one or more cavitiesdisposed along its length. The cavities generally are located in thestrip fastener so that they are disposed between the skull flap and theskull when the strip fastener is implanted in a patient. For example,the cavity may have a uniform cross section along the entire length ofthe strip fastener such as in the shape of a U, V, J, W or pleats orcorrugations or it may be a closed tube having the cross-sectional shapeof a circle, oval, ellipse, square, rectangle, triangle or any otherclosed geometric shape. The outer width of these cross-sections issometimes referred to herein as the outer width of the channel.References to such strip shapes herein each refer to the shape of across-section taken transverse to the length of the strip fastener. Inother embodiments one or more tubular elements are disposed on theunderside of the strip fastener and these are disposed between the skullflap and the skull when the strip fastener is implanted in a patient.

The surgical strip fasteners, including those with cavities or tubularelements, have side portions which are disposed between the skull flapand the skull when the strip fastener is implanted. These side portionscan have openings such as holes, slits or lateral slots which permitbone regrowth or these openings can be used to secure the strip to theedge of either the skull flap or skull by means of adhesives, glues,screws, tacks, staples, etc. Additionally the slits may be orientedalong a transverse axis through one sidewall and a portion of the bottomsection of the strip, allowing the strip additional flexibility. Thecavities also have a bottom portion and the tubular elements have bottomand top portions and these bottom and/or top portions also can haveopenings such as holes or lateral slots.

As a further option the cavities or tubular elements can be filled orpartially filled with medication, bone paste, bone growth enhancers andthe like.

The cranial plugs of the invention are used to plug small circularopenings in the skull such as those made by a surgeon to gain access forsurgery or to insert a cutting instrument such as a craniotome to cutout a skull flap. Sometimes more than one small hole is made in theskull to facilitate cutting out a skull flap and, following surgery, thecranial plugs can be used to fill each of those holes, sometimesreferred to as burr holes. The cranial plugs can be used by themselves,in combination with the strip fasteners of the invention or incombination with other fasteners. Some of the cranial plug designs alsocan be filled or partially filled with medication, bone paste, bonegrowth enhancers and the like.

Other variations and embodiments are described in more detail below andin the drawings and further variations will be apparent to those skilledin the art based upon the principles of the invention set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings are not intended to illustrate every embodiment ofthe invention but they are representative of embodiments within theprinciples of the invention. The drawings are for illustrative purposesand are not drawn to scale.

FIG. 1 is a representative view of a human skull showing one possiblelocation and configuration of a craniotomy skull flap.

FIGS. 1A and 1B are section views of portions of skull bone and cranialcavity.

FIG. 2 is a perspective view of one embodiment of a strip fastener ofthe present invention in a pre-use state and FIG. 2A is a section viewof the FIG. 2 embodiment.

FIG. 2B is a perspective view of variant of the FIG. 2 embodiment andFIG. 2C is a section view of the FIG. 2B embodiment.

FIG. 3 is a perspective view of an embodiment of a strip fastener of theinvention having a perforated, U-shaped, flexible strip and “U-shaped”clips and FIG. 3A is a section view of the FIG. 3 embodiment.

FIGS. 3B, 3C and 3D illustrate a series of steps for reattaching arepresentative skull flap to a skull using the strip fastener of FIG. 3.

FIG. 4 is a perspective view of another embodiment of a strip fastenerof the invention having a perforated, U-shaped, flexible strip and FIG.4A is a section view of the FIG. 4 embodiment. In this design, the“U-shaped” strip has integral tabs.

FIGS. 4B and 4C illustrate the FIG. 4 embodiment with an added elementfor strength and/or drug delivery.

FIG. 5 is a perspective view of an embodiment of a strip fastener of theinvention having a V-shaped flexible strip and FIG. 5A is a section viewof the FIG. 5 embodiment.

FIG. 5B is a perspective view of the FIG. 5 embodiment which is straightrather than pre-curved.

FIG. 6 is a perspective view of an embodiment of a strip fastener of theinvention having a W-shaped flexible strip and FIG. 6A is a section viewof the FIG. 6 embodiment.

FIG. 7 is a perspective view of an embodiment of a strip fastener of theinvention having a compression rib and FIG. 7A is a section view of theFIG. 7 embodiment.

FIG. 8 is a perspective view of a strip fastener of the invention havinga flexible strip comprised of three stacked tubes and FIG. 8A is asection view of the FIG. 8 embodiment.

FIGS. 8B and 8C are perspective views of flexible tubular strips whichcan be used in combination with the brackets 32 of FIG. 3 to make astrip fastener. In FIG. 8C the tubular strip has a helical slit alongits length.

FIG. 9 is a perspective view of a strip fastener of the inventioncomprising an inverted U-shaped flexible strip and FIG. 9A is a sectionview of the FIG. 9 embodiment.

FIG. 10 is a perspective view of a strip fastener of the inventioncomprising a barbed flexible strip and FIG. 10A is a section view of theFIG. 10 embodiment.

FIG. 11 is a perspective view of a cranial plug of the inventioncomprising flexible legs for a snap-fit and FIGS. 11A and 11B are a topview and section view, respectively, of the FIG. 11 embodiment.

FIG. 12 is a perspective view of another cranial plug and FIGS. 12A and12B are a top view and a section view, respectively, of the FIG. 12embodiment.

FIG. 12C is an expanded view of the FIG. 12 embodiment and FIG. 12D is asection view of the FIG. 12 embodiment in a use condition.

FIG. 13 is a perspective view of a cranial plug which can be snap-fit orinserted with a compression tool and FIGS. 13A and 13B are top views andsection views, respectively of the FIG. 13 embodiment.

FIG. 14 is a perspective view of a cranial perforation closure and FIG.14A illustrates the same closure after it has been bent to fill a burrhole. FIG. 14B is a section view of FIG. 14A.

FIG. 15 is a representative view of a human skull having installedtherein at one location the strip fastener of FIG. 3 and the cranialplug of FIG. 11 and at another location the strip fastener of FIG. 8Band three of the cranial plugs of FIG. 25.

FIG. 15A is a section view taken at section line 15A of FIG. 15illustrating the relationship of the strip fastener to the bone of theskull.

FIGS. 15B, 15C and 15D are section views taken at section line 15B ofFIG. 15 showing the relationship of the cranial plug to the bone of theskull and illustrating various skull bone types and thicknesses.

FIG. 16 is a perspective view of a cranial plug having top and sideopenings and FIGS. 16A and 16B are top views and section views of theFIG. 16 embodiment.

FIG. 17 is a section view of the plug of FIG. 16 and the strip fastenerof FIG. 3 in a use state and FIG. 17A is a perspective view of FIG. 17.

FIG. 18 is a perspective view of a cranial plug with two legs which canbe inserted after any of the strip fasteners with tabs have beenimplanted. It straddles the strip and covers the burr hole. FIGS. 18Aand 186 are a top view and a section view, respectively, of the FIG. 18embodiment.

FIG. 19 is a perspective view of a combination of a plug and a stripfastener. The two are combined into a single implant. FIGS. 19A and 19Bare a top view and a section view of the FIG. 19 embodiment.

FIG. 20 is a perspective view of another cranial plug and FIGS. 20A and20B are a top view and section view, respectively, of the FIG. 20embodiment.

FIG. 21 is a perspective view of still another cranial plug and FIG. 21Ais a section view of the FIG. 21 embodiment.

FIG. 22 is a perspective view of a cranial plug with a locking mechanismand FIG. 22A is a section view of the same. FIG. 22B illustrates theFIG. 22 embodiment in an in-use condition.

FIG. 23 is a perspective view of a cranial plug and FIG. 23A is asection view of the FIG. 23 embodiment.

FIG. 24 is a perspective view of a cranial plug. FIG. 24A is a top viewand FIG. 24B is a section view of the FIG. 24 embodiment.

FIGS. 24C and 24D are perspective views of alternatives to the FIG. 24embodiment.

FIG. 25 is a top perspective view of a cranial plug having a cam lock.FIG. 25A is a bottom perspective view of the FIG. 25 embodiment and FIG.25B is a top view. FIGS. 25C and 25D are section views of the FIG. 25embodiment installed in a skull.

FIG. 26 is a perspective view of a cranial plug having flexible vanes.FIG. 26A is a bottom view, FIG. 26B is an elevation view and FIG. 26C isa section view of the FIG. 26 embodiment.

FIG. 27 is a perspective view of a strip fastener having lateralcorrugations and FIG. 27A is a section view thereof. FIG. 27B is asection view of the FIG. 27 embodiment.

FIG. 28 is a perspective view of a strip fastener having longitudinalcorrugations. FIG. 28A is a top view of the FIG. 28 embodiment and FIG.28B is a section view thereof.

FIG. 29 is a perspective view of a cranial plug having flexible ribs.FIGS. 29A and 29B are a bottom view and a section view, respectively.FIG. 29C is a perspective view of an alternate embodiment of the FIG. 29plug and FIGS. 29D and 29E are a top view and a section view,respectively, of the alternate embodiment. FIG. 29F illustrates the FIG.29 plug in perspective in relationship to a skull flap and FIGS. 29G and29H illustrate the FIG. 29 plug installed in a skull.

FIG. 30 is a perspective view of a strip fastener of the inventionhaving a perforated, J-shaped, flexible strip. FIG. 30A is a top viewand FIG. 30B is a section view of the FIG. 30 embodiment.

FIG. 31 is a perspective view of a fastener of the invention which isused in conjunction with strip fasteners, for example, as illustrated inFIG. 30. FIG. 31A is a bottom view and FIGS. 31B and C are section viewsof the FIG. 31 fastener.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For reference, a human skull 1 with a craniotomy skull flap 2 is shownin FIG. 1. The skull flap 2 is defined by a burr hole 3 and theconnecting osteotomy cut 4, wherein the skull portion of the burr holeis designated in FIG. 1 as 3 a and the skull flap as 3 b. The skull flap2 has a perimeter contour 5 but it need not be of the particular shapeshown and may have any number of burr holes 3. (See FIG. 15 for a 3 burrhole configuration.) On the opposing sides of the osteotomy cut 4 is therespective bone edge surface 6 of the skull flap 2 and the surroundingbone 7 of the skull 1, respectively. The bone edge surface 6 has aperimeter contour 5 generally matching the contour of the surroundingbone 7 of skull 1.

The skull 1 and skull flap 2 are either made from bone that has a threelayer composition, as shown in FIG. 1A, or a single layer as shown inFIG. 1B. Referring to FIG. 1A, the outermost layer is the outer corticalbone 8 and the innermost layer is the inner cortical bone 9. Betweenthese two stiff layers is a relatively soft middle layer of cancellousbone known as the diploe 10. Interior to the inner cortical bone 9 isthe cranial cavity 11 housing the brain 12 and its surrounding duramatter 13. FIG. 1B illustrates the condition wherein the skull bone iscomprised entirely of cortical bone 14.

The present invention is particularly adapted for securing a craniotomyskull flap 2 to the skull 1, but may be used in other situations whereappropriate. The present illustrative discussion assumes that a stripfastener of the invention is being used to close a craniotomy skull flap2 having one burr hole 3 but the same principles apply if the surgeonmakes more than one burr hole in order to open up the skull for surgery.The osteotomy cut 4 may be normal to the surface of the skull 1 or at anangle thereto.

The term “strip fastener” is used herein to mean a surgical stripfastener of the invention and the term “plug” is used to mean a cranialplug (sometimes alternatively designated as a cranial perforationclosure) of the invention.

The strip fasteners of the invention can be made straight or with aprecurvature to reduce kinking when they are shaped to follow theperimeter contour of the skull flap.

The strip fasteners and plugs of the invention can be made of variousbiocompatible materials and combinations of biocompatible materials.Suitable materials include tissue friendly metals, alloys, plastics andreinforced plastics which are commonly used in surgical implants of allkinds. Such materials include materials that have sufficient strengthand flexibility to meet the objectives of the invention. The materialsalso can optionally be porous, semi-porous or semi-permeable. Many ofthe materials that have been approved by the United States Food and DrugAdministration (FDA) for surgical implant applications are alsosuitable.

Generally speaking, there are three main types of alloys used inbiocompatible metals today, titanium alloys, cobalt alloys and stainlesssteel alloys. An exhaustive list is available on the FDA website whichalso provides the reference numbers and effective dates of the ASTM orISO standards for many of the materials that are suitable. Some examplesinclude unalloyed titanium and titanium alloyed with aluminum, niobiumand/or vanadium; stainless steel and other irons alloyed withmolybdenum, chromium, cobalt, tungsten, aluminum, nickel, manganese orvanadium in various combinations, various other stainless steels andother iron alloys, for example, with aluminum oxides, zirconium oxides;tantalum and calcium phosphates. This list is not intended to beexhaustive.

Numerous types of high strength polymers also are employed to makeimplants and many of these are identified not only on the FDA websitementioned above but also on the ASTM website. Examples of suitable highstrength polymers include polyetheretherketone (PEEK), epoxys,polyurethanes, polyesters, polyethylenes, vinyl chlorides, polysulfones,polytetrafluoro-ethylene (PTFE), polycarbonates, polyaryletherketone(PAEK), polyoxymethylene, nylon, carbon fiber polyester,polyetherketoneetherketoneketone (PEKEKK), silicones, hydrogels and thelike. When a polymer is used, a small wire or other radiopaque materialcan be incorporated in the main body of the base for purposes of x-raydetection.

The foregoing lists of materials may have application in someembodiments of the present invention but not in others as will beapparent to those skilled in the art based on requirements of strength,flexibility, machinability and the like for the particular application.The lists are intended to be illustrative and not exhaustive. Othermaterials and new materials may be employed based upon the principles ofthe invention as set forth herein.

For purposes of this specification, the term “high strength polymer(s)”is defined as any tissue-friendly non-bioabsorbable polymer, copolymer,polymer mixture, plastic or polymer alloy having sufficient strength towithstand without failure the stresses that a fastener of the inventionwould normally be subjected to during surgery or in the body.

Bioabsorbable material can also be used to make all or a portion of oneor more of the component parts of the strip fasteners or plugs of theinvention and/or the bioabsorbable material can be applied as a partialor complete coating on such component parts.

The term “bioabsorbable material” as used herein includes materialswhich are partially or completely bioabsorbable in the body.

Suitable bioabsorbable materials include collagen, polyglycolide,poly(lactic acid), copolymers of lactic acid and glycolic acid,poly-L-lactide, poly-L-lactate; crystalline plastics such as thosedisclosed in U.S. Pat. No. 6,632,503 which is incorporated herein byreference; bioabsorbable polymers, copolymers or polymer alloys that areself-reinforced and contain ceramic particles or reinforcement fiberssuch as those described in U.S. Pat. No. 6,406,498 which is incorporatedherein by reference; bioresorbable polymers and blends thereof such asdescribed in U.S. Pat. No. 6,583,232 which is incorporated herein byreference; copolymers of polyethylene glycol and polybutyleneterephthalate, and the like. The foregoing list is not intended to beexhaustive. Other bioabsorbable materials can be used based upon theprinciples of the invention as set forth herein. Some of the mostcommon:

Poly-L-lactic acid (PLLA) Poly-DL-lactic acid (PDLLA) Polyglycolic acid(PGA) Polydioxanone (PDS) Polyorthoester (POE) Poly-C-capralactone (PCL)

Bioactive materials can be admixed with the bioabsorbable materials,impregnated in the bioabsorbable materials and/or coated on the outersurface thereof. Bioactive materials, including natural and/or syntheticmaterials, also can be used to fill cavities in the strip fasteners orcranial plugs. These materials can include, for example, bioactiveceramic particles, bone chips or paste, platelet rich plasma (PRP),polymer chips, synthetic bone cement, autologous materials, allograft,cadaveric materials, xenograft, nanoparticles, nanoemulsions and othermaterials employing nanotechnology, capsules or reinforcement fibers.And they can contain, for example, antimicrobial fatty acids and relatedcoating materials such as those described in Published U.S. PatentApplication No. 2004/0153125 A1; antibiotics and antibacterialcompositions; immunostimulating agents; tissue or bone growth enhancersand other active ingredients and pharmaceutical materials known in theart.

The products of the invention which are made with bioabsorbable materialcan be made by molding, extrusion, heat shrinking or coating thebioabsorbable material on a base which has been provided with attachmentmeans such as those described in our pending patent application Ser. No.11/025,213 filed Dec. 29, 2004 which is incorporated herein byreference. Some of the screws and other fastening devices described inour pending patent application Ser. No. 11/025,213 filed Dec. 29, 2004can also be used in or in combination with the strip fasteners andcranial plugs of the present invention. When the bioabsorbable materialwill have functional mechanical properties which are not made from thebase material, the bioabsorbable material can be molded onto the base inthe desired shape. Alternatively, the bioabsorbable material also can becoated, shrink wrapped or molded onto the base. If necessary, thebioabsorbable material can be machined to the desired shape and/ordimensions.

As will be apparent to those skilled in the art, the sizes of the stripfasteners and plugs of the invention can be varied to meet theirintended applications. The shapes can take various forms in addition tothose illustrated without deviating from the principles of theinvention. And the sizes, lengths and widths can be varied forparticular applications within the principles of the invention set forthherein.

Various methods can be used to employ the strip fasteners and/or cranialplugs of the invention as will be apparent to those skilled in the artbased upon the embodiment(s) of the fasteners and/or plugs selected foruse by the practitioner. For example, the strip fastener may be attachedto the skull flap first, then the skull flap and strip would bepositioned in the skull opening and the strip fastener would then beattached to the skull. This would be followed by affixing one or morecranial plugs in the burr hole or holes as needed. In most embodimentsantibiotics, bone growth enhancers or other materials disclosed hereincould be added in cavities in the strip fastener and/or plugs before orafter the skull flap is reattached to the skull, as will be apparent tothose having ordinary skill in the art. Another method would be toreattach the skull flap using the cranial plugs followed by attachmentof the strip fastener(s). In situations where three or more burr holesare created, the surgeon could choose to install a plug in each partialburr hole in the flap, affixing the flanges or the side sections of theplug to the top surface of the flap or edge of the flap respectively.The flap with the affixed plugs could then be inserted back into theskull and the plugs could provide a “snap-fit” or “press-fit” in theirrespective burr holes and/or the flanges could be affixed to the topsurface of the skull. In such situations, the surgeon may choose not touse strips in addition to the plugs. It should be noted that the term“affixing” as used herein includes “snap-fit” and “press-fit” as well asthe other means such as screws, staples, tacks, adhesives and the likedescribed herein. In still another method, the cranial plugs can holdthe strip fasteners in place while reattaching the skull flap or can beused in conjunction with strips to fixate the flap. Other methods willbe apparent to those having skill in the art depending upon the type ofstrip fastener(s) or plug(s) selected by the practitioner, thecharacteristics of the skull and/or skull flap, the type of surgeryinvolved and the likelihood or unlikelihood of the need to re-open thesurgical site.

As noted above, the strip fasteners of the invention can be formedaround the perimeter contour of the skull flap and attached to the skullflap before attachment to the skull. The step of attaching the fastenerto the skull flap can be done by operating room personnel while thesurgeon is performing surgery. This saves substantial time when theskull flap is reattached following surgery. The previously attachedstrip fasteners support the skull flap and insure that the top of theflap coincides with the top surface of the skull. When cranial plugs areused in combination with the strip fasteners, they can be installedbefore or after the skull flap has been reattached to the skull. If morethan one burr hole is used to make the cranial flap, the strip fastenermay be cut and attached in sections to the skull flap to leave room fora cranial plug at each burr hole. Alternately the strip portion of thestrip fastener may be threaded through one or more cranial plugs priorto attachment to the skull flap and the strip fastener may beessentially continuous around the entire kerf. Another option would beto use a combined strip fastener and plug implant as shown in FIG. 19,particularly in cases where only a single burr hole is created. As notedabove, the shape of the skull flap is highly variable and when it isreattached to the skull it is positioned in a manner to match theposition from which it was removed, similar to replacing a piece of ajigsaw puzzle.

There are numerous suitable options for fastening the strip fasteners ofthe invention to the skull flap and the skull. These include screws,staples, tacks, glues, adhesives, peel off adhesives, press-fit,snap-fit and combinations of two or more thereof. For example, a stripfastener may be stapled onto the skull flap and then press-fit into theopening in the skull. These fastening methods may be used to affix thestrips and plugs to any contacting surface of either the skull flap orskull. In some cases it might be preferable to secure the tabs of thestrips or the flanges of the plugs to the top surfaces of the skull orskull flap. In other instances the surgeon may choose to affix thesidewall of the strip or plug to the respective edges of the skull orskull flap.

For the embodiment illustrated in FIGS. 2 and 2A, the strip fastener 20is comprised of a strip 21 which is pre-curved and sufficiently flexibleto be shaped to follow the perimeter contour of a skull flap. Flap tabs22 are disposed on the bottom side of strip 21 and are arranged forattachment to the underside of the skull flap such as by using screwsthrough holes 23 or staples or adhesives or other suitable means knownin the art. Skull tabs 24 are for attachment to the outer surface of theskull. When the strip fastener 20 is attached to the skull, tabs 24 arefolded outwardly onto the skull outer surface and are fastened eitherusing screws through holes 25 or staples or adhesives or other suitablemeans known in the art. Strip 21 can optionally be perforated with holes27 and/or slots (not shown) such as those illustrated in otherembodiments of the invention, for example, in FIGS. 5 and 6 or slits(not shown) as illustrated in FIG. 8. When this strip fastener isemployed, it can either be attached first to the skull flap or theskull. Of course, if it is attached to the skull first, an adhesive orsimilar material will be used to attach it to the skull flap. Inaddition, the cross-section of the strip can be “L” shaped between theinner tabs 23 as illustrated in FIGS. 2B and 2C to provide a “floor”created by tabs 26 for containing the previously mentioned bioactivematerials used to fill portions or all of the kerf and promote fusion ofthe flap to the skull.

FIGS. 3 and 3A illustrate a strip fastener 30 comprised of a U-shapedstrip 31 which is pre-curved and sufficiently flexible to be shaped tofollow the perimeter contour of a skull flap. Brackets 32 may be adheredto the strip fastener 30 by adhesives, spot welding or other meanssuitable for the materials of which the strip 31 and brackets 32 arecomprised or they may be only movably retained and able to slide alongthe length of the strip 31. In another embodiment they may be separateitems, composed of the same or different material as the strip 31. Inthis case they would allow the surgeon the option, for example, ofattaching only the brackets to the skull flap before it is replaced intothe skull opening as illustrated in FIG. 3B. As illustrated in FIG. 3C,flap screws 33 and skull screws 34, adhesive or other means are used toattach the brackets 32 to the outer surfaces of the skull flap 35 andthe skull 39, or alternately to the edges of the skull or skull flap.Following the step illustrated in FIG. 3C, the strip 31 is inserted asshown in FIG. 3D. It is also conceivable that there may be circumstanceswhere the skull flap with attached fasteners is a “press fit” into theskull defect and no screws, staples, adhesive, etc. are necessary toattach to the skull. It is understood that these circumstances may beapplicable to many of the embodiments of the surgical fasteners of theinvention as will be apparent to those having skill in the art, forexample, when the outer width of the channel is sized for a press-fitinto the kerf.

Multiple holes 36 are disposed around the inside perimeter 37 and theoutside perimeter 38 of U-shaped strip 31. The holes 36 permit bonegrowth for bone to bone reattachment of the skull to the skull flap orthey can be used to affix the sidewalls of the strip to the edges of theskull flap. Bone growth can be enhanced by filling the U-shaped strip 31with known bone growth enhancers and/or other bioactive materials asdescribed above. This can be done before and/or after the strip fastener30 is implanted in the patient. This concept can be adapted by thoseskilled in the art to strip fasteners of other cross sections disclosedherein.

The strip fastener 40 illustrated in FIGS. 4 and 4A is a variation ofthe FIG. 3 embodiment having a U-shaped strip 41 which is pre-curved andsufficiently flexible to be shaped to follow the perimeter contour of askull flap. Flap tabs 42 and skull tabs 43 are disposed on the opensides of the inside perimeter 47 and outside perimeter 48, respectively,of the U-shaped strip 41. The tabs 42 and 43 are adhered to the skullflap and skull with adhesives, screws, staples or other suitable meansknown in the art. Multiple holes 46 serve the same function as describedin respect of the FIG. 3 embodiment and the U-shaped strip 41 can befilled with known bone growth enhancers and/or other bioactive materialsas described above. The outer width of the channel formed by theU-shaped strip 41 is such that it can require some level of compressionto seat the flap or it can be sized such that it is slightly thinnerthan the kerf so that only the tabs contact the skull when the flap isreplaced.

FIGS. 4B and 4C illustrate an added element 49 which can be astrengthening member and/or a tube filled with medication, bioactivematerials, bone growth enhancers and the like. Element 49 can be used incombination with several other embodiments of the invention such as theembodiments illustrated in FIGS. 2, 3, 5, 6 (if element 49 is soft andcan be pressed in), 7, 9 and 19. Alternatively, element 49 can be usedas a bending insert which is used to prevent a flexible strip fromspringing back or otherwise returning to its original shape as thesurgeon contours the strip to the osteotomy cut. In this alternativeembodiment the element 49 can be removed and discarded after the stripfastener is implanted in the patient.

FIGS. 5 and 5A illustrate a strip fastener 50 comprised of a V-shapedstrip 51 which is pre-curved and sufficiently flexible to be shaped tofollow the perimeter contour of a skull flap. Flap tabs 52 and skulltabs 53 are disposed on the open sides of the inside perimeter 57 andthe outside perimeter 58, respectively, of the V-shaped strip 51. Thetabs 52 and 53 can be adhered to the skull flap and skull with adhesive,screws, stapes or other suitable means known in the art or they can beused to locate the strip relative to the top surface of the skull orskull flap if it is affixed through the sidewall to the edge of theskull flap. (This is a common theme of the present invention in respectof the strips and is applicable to many of the plugs as well.) Multipleslots 56 serve the same function as the holes 36 described in respect ofthe FIG. 3 embodiment and the V-shaped strip 51 can be filled with knownbone growth enhancers and/or other bioactive materials and/ormedications as described above. FIG. 5B is a perspective view of theFIG. 5 embodiment which has not been pre-curved.

The strip fastener 60 illustrated in FIG. 6 is comprised of a W-shapedstrip 61 which is pre-curved and sufficiently flexible to be shaped tofollow the perimeter contour of a skull flap. Flap tabs 62 and skulltabs 63 are disposed on the open sides of the inside perimeter 67 andthe outside perimeter 68, respectively, of the W-shaped strip 61. Thetabs 62 and 63 are adhered to the skull flap and skull with adhesives,screws, staples or other suitable means known in the art. Slots 66 orholes (not shown) can optionally be provided through the W-shaped stripto serve the same functions as described above.

FIG. 7 illustrates a strip fastener 70 comprising a U-shaped strip 71which is pre-curved and sufficiently flexible to be shaped to follow theperimeter contour of a skull flap. Flap tabs 72 and skull tabs 73 aredisposed on the open sides of the inside perimeter 77 and the outsideperimeter 78, respectively, of the U-shaped strip 71. A compression rib75 is disposed on the closed end of the U-shaped strip 71 and multipleholes 76 are disposed around the inside perimeter 77 and outsideperimeter 78 of the U-shaped strip 71. In this embodiment the skull flapis first affixed to the strip fastener 70 by means of the tabs, with thecompression rib on that side in contact with the skull flap. The skullflap and fastener are then snap fit into place in the skull. Of course,adhesives, screws, staples or other means known in the art can be usedto secure the attachment to the skull flap and skull if deemed necessaryby the surgeon and optional fastener holes 74 are illustrated tofacilitate attachment.

Strip fastener 80 illustrated in FIG. 8 is comprised of one or moreflexible tubular strips 81 (three illustrated) which are pre-curved andsufficiently flexible to be shaped to follow the perimeter contour of askull flap. The term tubular as it is used herein is not meant torestrict the lateral cross-section of the tube to only a circularprofile. Oval, elliptical, rectangular or other closed geometric shapedtubular structures (not shown) are also within the meaning of “tubular”and can be used with this design. Tabs 82 are affixed to the tubularstrips 81 for attachment to the skull flap and the skull such as bymeans of adhesives, screws, staples or other means known in the art.Multiple slits 84 or holes or slots (not shown) can optionally beprovided in the tubular strips 81 as with many of the other embodimentsdiscussed above. The slits 84 are narrow cuts made through the strips81. The tubular strips 81 also can be filled with known bone growthenhancers and/or other bioactive materials as described above before theskull flap is reattached to the skull. These tubular strips may bepackaged (sterile) with the bioactive materials already filling thecavities. This is also possible for the other configurations butobviously much more practical for a tubular profile.

Many of the strip fasteners of the invention can be made without tabsfor attachment to the skull flap and skull and instead they can becombined with brackets such as bracket 32 illustrated in FIG. 3. Thetubular strip fasteners of FIGS. 8B and 8C are illustrative. Asdiscussed above in respect of the tubular strip fastener of FIG. 8, thetubes of FIGS. 8B and 8C can have various cross sections. In FIG. 8B,tube 86 of strip fastener 85 can be made from a solid, porous,semi-porous or semi-permeable material and/or it can have holes or slotsor slits.

Strip fastener 87 in FIG. 8C is comprised of a tube 88 having a helicalslit 89 which runs the entire length of the tube.

Multiple tubes of the kind illustrated and described in respect of FIGS.8B and 8C can be arranged together. For example, they can be stacked asin FIG. 8 or arranged in rows or combinations of rows and stacks or thelike. Combinations of tubes 86 and 88 can also be used in such multipletube embodiments. Tubes may also be made in a rolled form and bonegrowth enhancers and/or medications can be incorporated into the rolledtubular strip. These rolled strips may be sufficiently flexible (orsoft) such that they readily conform to the size and shape of the kerfwhen inserted in a patient's skull.

FIG. 9 illustrates a strip fastener 90 comprising an inverted U-shapedstrip 91. Closure strip 93 comprising tabs 92 is disposed on the closedend of the U-shaped strip 91 and the strips 91 and 93 are pre-curved andsufficiently flexible to be shaped to follow the perimeter contour of askull flap. The inside perimeter 97 and outside perimeter 98 are biasedoutwardly in the directions of arrow 99 so that they can be compressedbetween the edges of the skull flap and the skull when the skull flap isreattached to the skull. Optional openings 95 are for the introductionof bioactive materials. Optional holes 96 or slits or slots (not shown)can also be disposed around the inside and/or outside perimeters 97 and98 as discussed above in respect of other embodiments.

A strip fastener 100 is illustrated in FIG. 10 and it comprises aflexible strip 101 having barbs 102, 103 and 104. Closure strip 105comprising tabs 106 is disposed on the upper side of flexible strip 101.Holes or slots (not shown) can optionally be provided in strip 101.

A snap-fit cranial plug 110 is illustrated in FIG. 11. The plug 110comprises a flange 111 having an upper surface 112, a lower surface 113and a central opening 116. Multiple legs 114 extend downwardly from thelower surface 113 and are disposed radially around central opening 116.A foot 115 extends from the distal end of each leg outwardly in adirection away from the central opening 116. The opening 116 can receivemedication and/or bone growth enhancers. FIG. 11A is a top view and FIG.11B is a section view of plug 110. Central axis x-x is illustrated inFIGS. 11A and 11B and this is typical of the central axes of the cranialplugs of the invention.

FIG. 12 illustrates in perspective another embodiment of a snap-fitcranial plug 120. A top view is provided in FIG. 12A and section viewsin FIGS. 12B and 12C. FIGS. 12, 12A and 12B illustrate the plug 120 in apre-use condition and FIG. 12C illustrates the plug 120 in a usecondition. Similar to the FIG. 11 embodiment, this plug has multiplelegs 124 radially disposed around a central axis x-x. An axiallymoveable inner ring 127 is forced down toward the bottom of the legs andin doing so, expands the legs 124 away from the central axis of plug 120and prevents the plug from dislodging when it is in use. Medicationand/or bone growth enhancers and the like can be inserted throughopening 128.

A cranial plug 130 is illustrated in FIG. 13 with a flange 131 and legscomprised of arcuate walls 132 having feet 133 extending outwardlytherefrom. The plug 130 can be snap-fit into a burr hole or a tool canbe inserted through openings 134 to compress the legs 132 inwardly whenthe plug is inserted into the burr hole. Then the compression isreleased and the legs move outwardly to secure the plug 130 in the burrhole. FIG. 13A is a top view and FIG. 13B is a section view of plug 130.The central axis is x-x.

FIG. 14 illustrates a cranial perforation closure 140. Shown in thestraight condition, it can also be provided pre-curved and furthershaped intraoperatively to conform to a burr hole as illustrated in FIG.14A. Tabs 141 on the top surface of strip 143 attach to the skull andthe skull flap. Lower tabs 142 overlap to form a floor or barrier toprotect the dura and the brain. The implanted closure 140 can then befilled with bone growth enhancers or medication. Holes 144 or slots orslits (not shown) can be provided in the side walls as previouslydisclosed. FIG. 14B is a section view of FIG. 14A.

FIG. 15 illustrates a skull 1 having a skull flap 2 which has beenreattached using strip fastener 30 (see FIG. 3) and cranial plug 110(see FIG. 11) which fills a single burr hole that was used to facilitatecutting out the skull flap 2. (See FIG. 1.) FIG. 15A is a section viewtaken at section line 15A of FIG. 15 illustrating strip fastener 30, theskull bone 1 and skull flap bone 2. As explained above in respect ofFIGS. 1A and 1B, different bone types may be encountered in the skull.FIG. 15A illustrates bone having cortical outer and inner portions 8 and9, respectively, and a cancellous portion 10. FIGS. 15B, 15C and 15D aresection views taken at section line 15B of FIG. 15 and illustratingcranial plug 110 implanted in skull 1. The side wall of the burr hole iscut when the kerf is made to cut out the skull flap 2, thus bisectingthe side wall into a skull flap side wall portion 16 and a skull sidewall portion 17, hereinafter referred to collectively as the side wallof the burr hole or cranial perforation. FIG. 15B illustrates the sametype of cortical and cancellous bone as illustrated in FIG. 15A whereasFIG. 15C illustrates a relatively thin cortical bone 14S and FIG. 15Dillustrates a relatively thick cortical bone 14T.

FIG. 15 also illustrates another skull flap 18 and this skull flap hasbeen reattached using strip fastener 85 (see FIG. 86) and brackets 32(see FIG. 3) in combination with three cranial plugs 250 (see FIG. 25)which fill three burr holes that were used to facilitate cutting out theskull flap 18. It should be noted that brackets such as brackets 32 orsimilar brackets can be used in combination with many of the stripfasteners of the invention and most embodiments of the strip fastenerscan be made without skull tabs or flap tabs if they are to be used incombination with brackets or other means to hold them in place.

FIGS. 16, 16A and 166 illustrate a cranial plug 160 with a bottom discshaped portion 161, a slotted top flange 162 and a central axis x-x.Tapered flexible arcuate walls 163 have one or more barbs 164 forengaging the sides of the cranial perforation (burr hole). As this plugis compressed in the burr hole, the slot 165 in the top flange 162narrows to conform the plug to the perforation. A large opening 166separates the side walls and passes through the entire body of the plug160. Any of the previously described strip fasteners can be threadedthrough this slot so that one or more plugs can be retained by the stripfasteners when they are attached to the skull flap. Alternately thesurgeon could attach brackets to the flap, insert it into the skull,insert the plug(s) into the burr holes and finally install the strip.(See FIGS. 36-3D.) Alternatively, the strip could be threaded throughthe plug(s) and then the strip and plugs would be inserted into theskull. The slot 165 in the top 162 of the plug 160 allows the strip tobe continuous around the perimeter of the skull flap. Holes or slots(not shown) can be provided in the side walls 163 and the slot in thetop 162 allows medication and/or bone growth enhancers to be used tofill the opening 166.

FIGS. 17 and 17A illustrate the cranial plug 160 and the strip fastener30 (see FIG. 3) in a use state having reattached skull flap 172 torepresentative skull 171.

FIGS. 18, 18A and 18B illustrate cranial plug 180 with a large open area181 between the opposing flexible arcuate walls 182. Barbs 185 areprovided for engaging the sides of the burr hole. Plug 180 can beinserted into a burr hole in cases where a cranial closure strip iscontinuous around the perimeter of the skull flap. The large open area181 between the side walls 182 allows the plug to straddle the strip.Holes or slots (not shown) can be provided in the side walls and opening183 in the top 184 allows medication and/or bone growth enhancers to beused to fill the open area 181. The central axis is x-x.

FIG. 19 illustrates a strip fastener 190 with an affixed cranial plug191 at one end of the strip 192. Surgeons who use only a singleperforation for a craniotomy could use such an implant to fill the burrhole and seal the kerf. Obviously multiple combinations of theaforementioned plugs and strips can be used to make embodiments similarto FIG. 19 with one affixed plug. Additional movable plugs can becombined with such embodiments when there is a need to fill more thanone burr hole.

FIGS. 20, 20A and 20B illustrate a cranial plug 200 with tapered flutes201 arranged radially about the central axis x-x. These flutes are thinand deformable such that when the plug is inserted into the burr hole,the flutes deform/conform to the walls of the perforation. The plug 200is shown with a solid core but could also be made as a hollow part. Thesolid or hollow embodiments could be made with side holes, slots orslits (not shown) to encourage bone growth and/or when the plug 200 isto be filled through opening 202 with medication or bone growthenhancers or the like.

FIG. 21 illustrates a cranial plug 210 comprising a cup 213 with anupper rim 214 and external tabs 211 extending therefrom. The tabs 211will rest upon or be affixed to the skull and flap. The cup 213 can thenbe filled with the appropriate additives, medications, bone growthenhancers, etc. Optional holes 212 are illustrated in the sides of thecup and these alternatively can be slots or slits (not shown).

FIGS. 22 and 22A illustrate a cranial plug 220 with legs radiallydisposed around central axis x-x similar to that shown in FIG. 12. Inthis design however, the axially moveable inner element 221 is pulledupward/outward to prevent the legs 224 from deforming inward. Shown as asolid, the inner element 221 could also be hollow. Once the innerelement 221 is moved to its final position adjacent the lower surface222 of flange 225, as illustrated in FIG. 22A, the removable stem 226can be snapped off below the level of the top 228 of the plug. View 22Billustrates the in-use condition of plug 220.

FIGS. 23 and 23A illustrate a cranial plug 230 having a central axisx-x, a frustoconical extension 235 with thin flutes 231 in the form offlexible circular vanes disposed thereon and oriented in planes parallelto the lower surface 233 of flange 232. Similar to the plug shown inFIG. 20, these thin flutes would deform/conform when inserted into theburr hole. Shown as a solid, it too could be provided with a hollow coreand cross holes/slots.

FIGS. 24, 24A, 24B, 24C and 24D illustrate a cranial plug 240 having acentral axis x-x, a cylindrical extension 245 and disposed thereon atapered helical thread 241 having a thin cross-section. It is designedto be rotated/screwed into the burr hole and it is expected that thethread will deform/conform to the bony side walls. Different drivemechanisms are shown. FIGS. 24, 24A and 24B illustrate a cruciform driveopening 242. FIG. 24C shows a hex drive opening 243 and FIG. 24D shows aspanner drive opening 244. Shown as solid plugs, they could also beproduced in hollow forms with cross holes, slots and/or slits (notshown).

FIGS. 25, 25A and 25B illustrate a cranial plug 250 with radiallydisposed legs 251 similar to those shown in FIG. 12 and FIG. 20. FIG. 25is a top perspective view, FIG. 25A is a bottom perspective view andFIG. 25B is a top view. In this case, a moveable inner cam 254 rotatesaround the central axis x-x so that it contacts the legs 251 to pushthem outward, holding them in the outward position and preventing themfrom deflecting inward. A cruciform drive recess 253 is shown but otherdrive mechanisms are possible. The figures illustrate plug 250 with cam254 in the pre-use position wherein the legs 251 have not yet beenpushed outwardly.

FIGS. 25C and 25D illustrate in section views the cranial plug 250 in ause condition. In FIG. 25C the skull flap 255 and skull 258 arerelatively thick and in FIG. 25D the skull flap 256 and skull 259 arerelatively thin.

FIG. 26 is a perspective view of cranial plug 260. FIG. 26A is a bottomview, FIG. 26B is an elevation view and FIG. 26C is a section view. Theplug 260 has a central axis x-x and flexible vanes 261 which press fitagainst the sides of a burr hole when plug 260 is in use. Optionalopening 262 in top 263 of plug 260 allows for medication to be insertedand optional floor disc 264 holds the medication in place. Optionalopenings 265 serve the same function as the holes, slits or slots inother embodiments of the plugs and strip fasteners of the invention.

FIG. 27 illustrates strip fastener 270 having lateral corrugations 271which facilitate bending without kinking. A top view is illustrated inFIG. 27A and a section view is illustrated in FIG. 27B. In a use state,the opening 272 is arranged so that medication and the like can easilybe added to fill the cavity 273. The fastener 270 has flap tabs 274 andskull tabs 275 for affixing the fastener to the skull flap and skull.Holes, slots or slits can be provided as with many of the other stripfastener embodiments of the invention.

FIG. 28 illustrates strip fastener 280 having longitudinal corrugations281 which facilitate bending and provide added surface area. A sectionview is illustrated in FIG. 28A. In a use state, the opening 282 isarranged so that medication and the like can easily be added to fill thecavity 283. The fastener has flap tabs 284 and skull tabs 285 foraffixing the fastener to the skull flap and skull. Holes 286 areillustrated but slots or slits can be provided alternatively or inaddition to the holes as with many of the other strip fasteners of theinvention.

A snap-fit cranial plug 290 is illustrated in FIGS. 29, 29A and 29B. Theplug 290 comprises a flange 291 having an upper surface 292, a lowersurface 293 and a central opening 296 concentric with central, axis x-x.Multiple flexible ribs 294 extend downwardly from the lower surface 293and are disposed radially around central opening 296. The ribs 294 areshaped to facilitate a snap-fit when the plug 290 is pushed into a burrhole. The proximal ends of the ribs 294 are affixed to the lower surface293 of the flange 291. As the ribs extend downwardly they taper awayfrom the central axis toward an elbow. At the elbow, the direction ofthe taper is turned inwardly toward the central axis and continues tothe distal ends of the ribs. Optionally, as shown in FIG. 29, a secondelbow is provided at the distal ends whereupon the ribs are taperedtoward the central opening 296 as the ribs approach the central axis.Optional holes 297 are provided for fasteners such as screws. Screws maybe used, for example, when the plug 290 is to be fastened at the burrhole portions of a skull flap. Then the skull flap can be snap-fit intothe skull without the need for additional fasteners. This is especiallyadvantageous in surgeries wherein the skull flap may need to be removedat a later date for additional surgery or diagnostic procedures.

FIGS. 29C, D and E illustrate snap-fit cranial plug 299 which is analternative embodiment of the FIG. 29 plug having a hinged lid 298thereon. Latch 295 on hinged lid 298 allows the lid to be snapped closedin order, for example, to prevent medication from coming out of thecentral opening of the plug or to prevent soft tissue from prolapsinginto the cavity. Obviously the cap could be entirely removable (nohinge) and secured by many of the same methods disclosed herein toretain a plug in a burr hole.

FIG. 29F illustrates in perspective a skull flap 35 wherein three plugs290 have been adhered at three burr hole portions disposed around theperimeter of flap 35. FIGS. 29G and 29H are top and section views,respectively, of the skull flap 35 installed in the skull 39 using theplugs 290. Section view FIG. 29H illustrates two of the burr holes, h1and h2. Kerf k can optionally be filled with one of the strip fastenersof the invention.

The strip fastener 300 illustrated in FIGS. 30, 30A and 30B is comprisedof a J-shaped flexible strip 301 which is pre-curved and sufficientlyflexible to be shaped to follow the perimeter contour of a skull flap.As with the other strip fastener embodiments of the invention, the stripfastener 300 can have integral tabs on the inside perimeter 307 or boththe inside perimeter 307 and the outside perimeter 308. This embodimenthas been illustrated with an elongate flange 302 which spans the cavityand forms a continuous tab on both the inside and outside perimeters. Avertical rib 304 connects the cavity to the flange 302. In thisembodiment, the vertical rib 304 purposely positions the J-shaped cavitybelow the level of the underside of the flange 303 to insure that theJ-shaped flexible strip 301 remains below the top surface of the skulland skull flap.

FIG. 31 illustrates a perspective view of a V-shaped bracket 310 with acontinuous elongate flange 311 creating tabs on both sides of the kerf.Optional fastener holes 312 are shown in each tab. A hollow, V-shapedsection 313 projects from the underside of the flange 314 and is meantto fit around a compatibly shaped flexible strip (without tabs). Inother words, the strip is threaded through the V-shaped section ofbracket 310. Optional tabs 315 on the inside of the hollow sectionposition the strip at a distance below the underside of the flange 314.These brackets could be affixed to the strip or could be able to slidealong its length. Obviously other strip cross sections (U, J, W,tubular) could be used in a similar manner.

1-19. (canceled)
 20. A cranial plug for a burr hole or a cranialperforation made in a skull during brain surgery, the burr hole orcranial perforation having side walls, comprising a flange having anupper surface, a lower surface and a central axis generallyperpendicular to the upper surface, and at least one extensionprojecting downwardly and away from the lower surface, wherein said atleast one extension is beside the side walls when the cranial plug isimplanted in a patient. 21-24. (canceled)
 25. The cranial plug of claim20 wherein said at least one extension comprises a plurality of flexiblelegs terminating at distal ends disposed away from the lower surface.26. The cranial plug of claim 25 wherein each leg has a foot at thedistal end extending outwardly and away from the central axis.
 27. Thecranial plug of claim 20 wherein said at least one extension comprises aplurality of flexible legs arranged radially about the central axis andequidistant therefrom and terminating at distal ends disposed away fromthe lower surface, further comprising a circular opening disposed in theflange coaxially with the central axis and a ring or a disc sized to fitthrough said circular opening, the ring or disc being movable to aposition at or near the distal ends whereby the ring or disc causes thedistal ends to be pushed outwardly and away from the central axis. 28.The cranial plug of claim 26 further comprising an opening disposed inthe flange over each foot.
 29. The cranial plug of claim 20 wherein saidat least one extension comprises two flexible arcuate walls disposedopposite one another, the arcuate walls having distal ends disposed awayfrom the lower surface and proximal ends affixed to the lower surface,the distal ends being connected with a bottom portion and the bottomportion being generally parallel with the lower surface, and the flangebeing cut into two pieces generally across a diameter disposed betweenthe proximal ends of the arcuate walls.
 30. The cranial plug of claim 29wherein the arcuate walls have outer surfaces with barbs disposedthereon.
 31. (canceled)
 32. The cranial plug of claim 20 wherein said atleast one extension is frustoconical and has a central axis which iscoaxial with the central axis of the flange, the frustoconical extensionhaving an axially fluted outer surface which tapers inwardly toward thecentral axis as the extension projects downwardly and away from thelower surface toward a distal end of the frustoconical extension. 33-35.(canceled)
 36. The cranial plug of claim 26 further comprising acircular opening in the flange arranged coaxially with the central axis,an axially moveable inner element having an upper surface and aremovable stem projecting upwardly therefrom, the inner element and stemhaving a central axis which is coaxial with the central axis of theflange wherein the stem can be pulled upwardly through the circularopening until the upper surface of the inner element is adjacent thelower surface of the flange whereby the inner element causes the legs tomove outwardly and press against the side walls.
 37. The cranial plug ofclaim 20 wherein said at least one extension is frustoconical, has acentral axis which is coaxial with the central axis of the flange andhas an outer surface which tapers inwardly toward the central axis asthe extension projects downwardly and away from the lower surface,further comprising at lease one flexible circular vane projectingoutwardly from the outer surface in a plane in parallel with the lowersurface.
 38. The cranial plug of claim 20 wherein said at least oneextension is a threaded cylinder having a central axis which is coaxialwith the central axis of the flange and the upper surface has a driveopening to facilitate rotating the plug about the central axis.
 39. Thecranial plug of claim 38 wherein the drive opening is selected from thegroup consisting of cruciform, hex and spanner.
 40. The cranial plug ofclaim 20 wherein said at least one extension comprises a plurality offlexible legs arranged radially about the central axis and equidistanttherefrom and terminating at distal ends disposed away from the lowersurface, further comprising a cam rotatable around the central axis andin contact with the legs whereby the cam can be rotated to cause theflexible legs to be pushed outwardly and away from the central axis. 41.The cranial plug of claim 20 wherein said at least one extension iscomprised of multiple vanes which taper inwardly toward the central axisas the vanes project downwardly and away from the lower surface towardtheir distal ends, the flange optionally having an opening therethrough.42. The cranial plug of claim 41 wherein the distal ends are affixed toa disc lying in a plane parallel to the plane of the lower surface andhaving a circumference defined by the circumference of a circleconnecting the distal ends, the flange optionally having an openingtherethrough.
 43. The cranial plug of claim 20 having multipleextensions projecting downwardly and away from the lower surface and acentral opening in the flange concentric with the central axis, themultiple extensions being disposed radially around the central opening,each extension having a proximal end affixed to the lower surface andbeing first tapered away from the central axis toward an elbow and thenbeginning at the elbow, being tapered toward the central axis untilterminating at the distal end.
 44. The cranial plug of claim 43 whereineach extension has a second elbow at the distal end whereupon theextension is tapered toward the central opening as it approaches thecentral axis.
 45. The cranial plug of claim 43 further comprising ahinged cover for the central opening.
 46. (canceled)
 47. A cranial plugfor a burr hole or a cranial perforation made in a skull during brainsurgery to facilitate cutting a skull flap out of the skull, the burrhole or cranial perforation having side walls, comprising a flexiblestrip which can be shaped to follow the contour of the side walls, thestrip having upper tabs which can be affixed to the skull and the skullflap and lower tabs which form a barrier when the plug is implanted inthe burr hole or cranial perforation.
 48. A cranial plug for a burr holeor a cranial perforation made in a skull during brain surgery tofacilitate cutting a skull flap out of the skull, the plug having a cupshaped portion with sides, a bottom and an upper rim, the sidesoptionally having holes, slits or slots disposed therein and the rimhaving outwardly disposed tabs which can be affixed to the skull and theskull flap and the bottom forms a barrier when the plug is implanted inthe burr hole or cranial perforation. 49-69. (canceled)